This invention is generally directed to novel telomeric quaternary salts, and more specifically, telomeric quaternary salts having a number average molecular weight of from about 1,000 to about 10,000. These salts are useful for example as charge enhancing additives for imparting positive charges to toner compositions, which toner compositions are employed together with carrier particles as developing materials in electrophotographic imaging systems. The toner and developer compositions containing the charge enhancing additive of the present invention are described and claimed in copending application identified, U.S. Ser. No. 259,789, filed on May 1, 1981, in the name of Roger N. Ciccarelli, the disclosure and examples of which are fully incorporated herein by reference.
While telomeric compositions, are known in the art, telomeric quaternary salts having a number average molecular weight of from about 1,000 to about 10,000 are not known, nor have they been isolated. Additionally, the use of such salts as toners and developers is not known in the art.
The electrophotographic process and more specifically, the xerographic process is well known, as documented in several prior art references. In these processes, an electrostatic latent image is developed by applying electroscopic particles or toner to the electrostatic latent image, using, for example, the cascade development method as described in U.S. Pat. No. 3,618,552, magnetic brush development as described in U.S. Pat. Nos. 2,874,063 and 3,251,706, or touchdown development as described in U.S. Pat. No. 3,166,432. In some instances, it may be desirable in such systems to produce a reverse copy of the original, thus, for example, it may be desired to produce a negative copy from a positive original, or a positive copy from a negative original.
In U.S. Pat. No. 3,893,935, there is disclosed the use of certain quaternary ammonium salts as charge control agents for electrostatic toner compositions. According to the disclosure of this patent, certain quaternary ammonium salts when incorporated into toner materials were found to provide a toner composition which exhibited relatively high uniform and stable net toner charge, when mixed with a suitable carrier vehicle. U.S. Pat. No. 4,079,014 contains a similar teaching with the exception that a different charge control agent is used, namely a diazo type compound.
Many of the described developers have a tendency to lose their positive charge over a period of time and in some instances, the charge enhancing additives employed are incompatible with the toner resin, thus making it difficult to uniformly disperse or dissolve such materials in the toner. Also, the charge control agents as described in U.S. Pat. No. 3,893,935 are soluble in water causing them to be leeched to the toner surface by moisture, thereby adversely affecting the machine environment in which they are used, and copy quality.
Some recently introduced commercial electrophotographic machines utilize organic photoconductors instead of inorganic photoconductors such as selenium, which photoconductors are charged negatively in comparison to selenium which is charged positively. Accordingly, toner materials containing a positive charge thereon are needed for causing the proper development of the images contained on the organic photoreceptor surface. While the prior art describes the use of charge control agents for imparting a positive charge to the toner resin, there continues to be a need for new materials which provide a high positive charging intensity to the toner resin, which intensity is maintained at relatively the same level over an extended period of time. Some charge control agents while they initially impart a positive charge to the toner resin, may not be capable of maintaining that charge over a long period of time, and further such charge control agents may be incompatible with the development system thereby adversely affecting the quality of the images developed. Also some of the prior art charge control agents are incompatible with the toner resin material which adversely affects the charge inducing properties of the charge control agent.
Accordingly, there is a need for new telomeric quaternary ammonium salts, which salts are of a specific molecular weight, thus enabling them to possess specific properties, particularly when such salts are used as charge enhancing additives for toner and developer compositions. Such toners and developer compositions can be used in reversal imaging systems particularly those systems wherein positively charged toner materials are required, which positive charge is substantially high and can be maintained over a long period of time, thus allowing the production of high quality images in an electrophotographic system.